One changing fabrics in launderette machine — not right (4)
I believe the answer is:
dyer
'one changing fabrics' is the definition.
(a dyer changes the colour of fabrics)
'launderette machine not right' is the wordplay.
'launderette machine' becomes 'dryer' (machine for drying clothes).
'not' indicates named letters should be taken away.
'right' becomes 'r' (common abbreviation).
'dryer' with 'r' taken away is 'DYER'.
'in' is the link.
(Other definitions for dyer that I've seen before include "colourist" , "Colourer (of clothes, perhaps)" , "Also a cleaner, probably" , "Increase (in output)" , "Fabric colourer" .)